Problem: $\left[\begin{array} {ccc} 9& 1\\ -3& 7\\ 7& 1 \end{array}\right]$ What are the dimensions of the matrix?
Answer: The first dimension is the number of rows in the matrix. There are $3$ rows. The second dimension is the number of columns in the matrix. There are $2$ columns. In conclusion, the dimensions of the matrix are $3\times 2$.